1. Field of Invention
The invention relates to a light driving apparatus and, in particular, to a digital controlled multi-light driving apparatus for a large size flat panel display or an illumination device.
2. Related Art
Flat panel displays have become increasingly popular in recent years, with liquid crystal displays (LCDs) garnering the most widespread acceptance. Conventional LCDs are typically employed as personal computer monitors and have a screen size of 15″ or less. As manufacturing technology has developed, a variety of display sizes have come to be employed for different purposes, including use as TV displays. When employed for this purpose, a flat panel LCD with a screen size of 30″ or larger is desirable. Accordingly, all LCD of this size requires a greater number of lights to provide adequate brightness. For example, an LCD with a screen size of 40″ may require up to 30 lights.
When the number of lights is increased, however, an accompanying problem of poor brightness uniformity between lights arises. In addition, the number of light driving apparatuses for driving the lights is also increased. For example, regarding the conventional light driving apparatus, usually only two cold cathode fluorescent lamps (CCFLs) can be driven at the same time by one transformer. Thus, for an LCD with a large screen size requiring increased number of lights, the number of required light driving apparatuses is also increased, and manufacturing costs thereof increase as a result.
As previously mentioned, the conventional LCD typically employs CCFLs as backlights thereof. To induce the CCFL or CCFLs to emit light, a light driving apparatus with an inverter is typically used. Referring to FIG. 1, a conventional tight driving apparatus 8 mainly includes a current adjusting circuit 81, an oscillation step-up circuit 82, a detecting circuit 83, and a feedback control circuit 84.
The current adjusting circuit 81 is controlled by the feedback control circuit 84 and properly adjusts an external DC source, which is then input to the oscillation step-up circuit 82. The oscillation step-up circuit 82 converts the input DC source into an AC signal and amplifies the AC signal. The amplified AC signal is then provided to the CCFL 9, which serves as the light, so that the CCFL 9 can then emit light. Furthermore, the detecting circuit 83 detects a feedback signal, such as a current signal or a voltage signal, from one end of the CCFL 9. The feedback signal is then transmitted to the feedback control circuit 84. The feedback control circuit 84 controls the current adjusting circuit 81 according to the feedback signal, so that the current adjusting circuit 81 can output a suitable current level. It should be noted that the conventional feedback control circuit 84 is an analog feedback control circuit.
When the number of lights is increased, the number of required light driving apparatuses 8 is increased accordingly. In an LCD with a large screen size, a plurality of circuits, each of which includes the current adjusting circuit 81, oscillation step-up circuit 82, detecting circuit 83 and feedback control circuit 84, are necessary at the same time. Since the lights are driven by different driving apparatuses 8, which are independent from one another, the brightness uniformity adjustment or phase matching between lights cannot be efficiently achieved, resulting in poor display quality.
Therefore, it is an important subjective to prevent the above-mentioned problems, so as to improve the quality of an LCD with a large screen size and reduce manufacturing costs. In addition, it is also an important subjective to improve the illumination efficiency.